//post提交 下载文件
function post(url, PARAMS) {  
	var formDom = $(document.createElement('form'));
    //var formDom = $("<form><form>");        
    formDom.attr("action",url);    
    formDom.attr("method","post");  
    formDom.hide();  
    for (var x in PARAMS) {        
        var textDom =$("<textarea><textarea>").attr("name",x).attr("value",PARAMS[x]);        
        formDom.append(textDom);
    }    
    formDom.hide();
    $("body").append(formDom);      
    formDom.submit();        
}